Space heater



J. UPTON SPACE HEATER April 12, 1938.

2 Sheets-Sheet 1 Filed Dec.

April 12, 1938. J UPTQN I 2,113,507

S PACE HEATER Filed Dec. 11, 19154 2 Sheets-Sheet. 2

w W l 4P0 AMLXLQ .91? &y W Va? Patented Apr. 12, 1938 PATENT OFFICE SPACE John Upton,

HEATER Wayland, Mass.

Application December 11, 1934, Serial No. 756,960

2 Claims.

This invention relates to an improvement in a heat exchanger having a plurality of tubes through which a heating medium is passed, the outer surfaces of the tubes being contacted by one or more streams of air or the like to change the temperature thereof, the term heat exchanger being used herein in its broadest sense to include all mechanism of this type by which an exchange of heat is attained.

One object of this invention is to provide a heat exchanger of maximum efficiency, the tubes and other parts through which the heating medium is passed being of a particular conformation whereby the maximum surface cont-act of the air or the like therewith is attained.

Another object of this invention resides in-the conformation and arrangement of such tubes.

These and other objects will be pointed out in the following description of two embodiments of my invention and shown in the accompanying drawings, in which Fig. 1 is an elevation of a heat exchanger embodying one form of my invention;

Fig. 2 is another elevation thereof taken at right angles to the elevation shown in. Fig. 1;

Fig. 3 is a sectional plan view thereof taken along the line 3-3 in Fig. 2;

Fig. 4 is an enlarged cross-sectional view of a typical tube of the space heater;

Fig. 5 is an enlarged perspective view of another element of the space heater.

Fig. 6 is an elevation of a space heater embodying another form of this invention; and

Fig. 7 is a plan view thereof, a part being broken away and shown in section.

For the purpose of illustrating this invention there are shown in the drawings and will be described, gas-fired high speed space heaters each having a combustion chamber, a stack and a 10 heat exchanger unit including a plurality of tubes which convey the products of combustion to the stack and which are adapted to raise the temperature of a flow of air brought into close contact therewith. It will be understood, however, that these space heaters are chosen solely for the purpose of illustrating this invention, and not in any way limiting it.

The space heater shown in Figs. 1 to 5 comprises a casing I D, rectangular in cross section, having an air inlet l2 and an air outlet l4. Enclosed within the casing is a gas combustion chamber 16 having a plurality of burners 11 therein supplied with gas through pipes 18 which enter a closed compartment 20 below the grate of the combustion chamber. The walls of the chamber l6 are rounded to conform to the profile of the gas flames so that the impingement of the flames on the wall is reduced to a minimum thereby holding the loss of heat units to the chamber wall to a minimum and maintaining the gases as they continue through the tubes at a higher temperature.

Each tube 22 has a head portion 26 and a tail portion 28, and is symmetrical in cross-section about an axis 30 parallel to the direction of the air flow. The head portion 26 comprises a segment of a symmetrical curve intersected at points equidistant from the axis 3|] by two segments of another symmetrical curve. These segments are connected to the tail portion 28, which is generally tapering and of such length that the axis 30 is longer than any axis of the tube perpendicular to the line of air flow. From the above description it will be apparent that the tubes are of an air foil or streamlined conformation in cross-section, and that air flowing in the direction of the axis 3!) will contact with the entire surface without creating eddies or dead air spaces.

Fig. 4 illustrates the form of tube I now be lieve to be the most efficient. As there shown, the head portion 26 comprises the segment 32 of a circle having its center 34 on the axis 30 and a radius 36 and the segments 38 of another circle having its center 40 on the axis 30 and a radius 42. The radius 42 is greater than the radius 36 and the center 40 is such a distance from the center 34 that the segments 38 will intersect the segment 32 and not be tangential thereto. The tail portion 28 comprises intersecting lines tangential to the circles of the head portion 26. The lines 44 are tangential to the large circle and if extended (as indicated in. dotted lines) would meet on the axis 30 at a point 46. The lines 48 are tangential to the smaller circle and meet on the axis 30 at a point 50. All the intersections preferably include small fillets except that the intersection. of the lines 48 may be either pointed or rounded. The lines 44 and 48 may be either straight lines or segments of curves whose radii are greater than the radius 42.

The tubes 22 are arranged in three groups, in two of which the products of combustion travel upward and in the other of which they travel downward. The air to be heated flows over all these tubes and in order to provide uniformity of space a partition 52 forming a part secured to the left wall of the casing is provided (see Fig. 1). The tubes are supported within the casing by cross plates 54, 56 and 58. As shown in Figs. 1 and 2 the plates 54 and 58 abut the partition 52 and the opposite wall of the casing, while the other edges are spaced from the casing walls to allow a flow of air around them. The plate 56 abuts the partition 52 and easing walls at three edges and is spaced therefrom at the fourth edge- This plate acts not only as a structural element but also as a battle to insure the proper travel of the air and will be hereafter so designated.

The air flow is set up by a blower 60 which draws the air through the inlet l2, over the sections of the tubes 22 above the baffle plate 56, around the edge of the baffle plate, and over the sections of the tubes below the baffle plate as well as over the walls of the combustion chamber, and forces the air so heated through the outlet M. The air, as indicated by arrows in Fig. 2, thus travels within the casing in two substantially opposite directions one above and the other below the bafile plate 56.

The tubes are so mounted that the air flows from the head to the tail of the tubes. The air thus contacts with the entire outer surface of the tubes, no dead air pockets or eddies being set up which would prevent such complete contact. In order to attain this arrangement the sections of the tubes above the baiile plate 56 are mounted with the heads to the right and those below the baflle plate with the heads to the left (see Fig. 2). The upper and lower sections are accordingly joined by adapters 62 (Fig. which are suitably fixed in the baille plate 56.

As shown in Fig. 1 the tubes of the different groups are connected by connecting headers 64 which conduct the products of combustion from the tubes of one group to those of the succeedin'g group. In the present instance these headers are formed by horizontal lengths of the tubes. The connecting headers 64 are at different levels, that connecting the first tube, beginning at the left, and the fourth tube being higher than that connecting the second and third tubes, and similarly that connecting the fourth and fifth tubes being higher than that connecting the third and sixth tubes. The tubes 22 themselves are laterally ofiset (see Fig. 3) for the same reason. The offset arrangement of the tubes and headers has been found of advantage in that the area through which the air flows unimpeded is reduced and consequently the body of the air is more uniformly heated. The rounded walls of the combustion chamber facilitate the passage of the air over the outer surfaces.

Figs. 6 and 7 illustrate the application of my invention to another form of space heater. The casing contains a combustion chamber 72, a plurality of tubes 74, connecting headers 16 and a stack 18. The tubes 14 are arranged in three groups, the products of combustion rising in the two outer groups and descending in the middle group. The number of tubes in each group is the same, six being here shown. The air flow in this embodiment is in one direction only, and the tubes are offset so that the air flows over each tube in the most efficient manner. The tubes 14 have the same generally air foil crosssectional conformation as the tubes 22 and since this has already been described in detail hereinabove further description is felt to be unnecessary.

The air flows over the tubes in the direction designated by the arrow at the left of Fig. 7. The tubes are relatively close together and the distance between the head portions is approximately one-half the distance between the tail portions. Consequently each pair of adjacent tubes functions as a venturi to increase the speed of travel of the air and insure a complete surface contact of the air upon the tubes.

The tubes instead of being connected by horizontal lengths as are the tubes 22, are connected by the headers 16. The headers each include a plurality of individual passages 80 (see Fig. 7) and have an outer surface, the form of which follows substantially that of the tubes 14. The combustion chamber 12 is of a similar conformation. No means is here shown to set up a flow of air, but it will be understood that any suitable well known means may be employed; for example, a blower as in the embodiment previously described.

The unit 82 carrying the chamber 12 is removably fixed in position in any suitable manner, as for example by the provision of straps 84 depending from the combustion chamber, and a strap 86 extending under the unit 82. The ends of the straps are brought into parallelism and united by wing nuts 88. The casing is supported upon legs 92 of sufiicient height so that the unit 32 when released may drop below the casing and be. removed without difficulty.

While certain embodiments of this invention have been shown and described, it will be understood that I am not limited thereby and that other embodiments may be made without departing from the spirit and scope thereof as set forth in the following claims.

I claim:

1. A space heater comprising a casing having an air inlet and an air outlet, a plurality of tubes of air-foil form, a baffle plate abutting the walls of the casing intermediate the inlet and outlet, the tubes extending at right angles to the baflle, each of said tubes having in cross section a head and a tail, the tubes at the side of the baflle plate adjacent the inlet being arranged with the head portions nearer the inlet than the tail portions and the tubes at the other side of the baffle plate being arranged with the tail portions nearer the outlet than the head portions and adapters carried by and projecting from the faces of the baflle plate connecting said tubes.

2. A space heater comprising a casing having an air inlet and an air outlet, a plurality of tubes of air-foil form, a baifie plate abutting the walls of the casing intermediate the inlet and outlet, the tubes extending at right angles to the baflle, each of said tubes having in cross section a head and a tail, the tubes at the side of the baffle plate adjacent the inlet being arranged with the head portions nearer the inlet than the tail portions and the tubes at the other side of the baille plate being arranged with the tail portions nearer the outlet than the head portions and adapters carried by and projecting from the faces of the baflle plate connecting said tubes, each of said adapters being so formed that the portion projecting from one face of the plate is the reverse of the portion projecting from the other face.

JOHN UPTON. 

